I have a late 2012 Mac Mini with Mountain Lion installed. I have had the Mini for around 6 weeks and am using as a media server.
When the Mini goes to sleep (either automatically or by manually telling it to) it refuses to wake up. The power light is pulsing.
The Mini is connected via HDMI to a home cinema receiver (which is in turn connected to a TV) and has an external USB hard disc and USB hub attached. There is a wireless keyboard and mouse attached via USB also.
In the Energy Saving preferences I have all tick boxes enabled apart from "put hard discs to sleep". I have tried the wireless keyboard, mouse and the Apple Remote app to wake the Mini to no avail.
Any ideas? I really need it to sleep and wake when needed as thats an essential feature of a media server.
Best Answer
Try resetting the NVRAM / PRAM as noted About NVRAM and PRAM
See if the sleep problem still occurs, if it does try resetting the SMC as noted Intel-based Macs: Resetting the System Management Controller (SMC).
If the problem still persists and you are running OS X Mountain Lion version 10.8.2, there may be a sleep bug that is effecting the reliability of sleep on a lot of Macs as discussed Problem with waking from sleep with 10.8.2
Since your Mac Mini is very new I would also consider contacting Apple Support and see what they offer as a solution and at the least notify them of the issue, I am sure they are working on a fix probably scheduled to be included with the next OS X update.